Conventionally, a surface protective layer and an interlayer insulating film for a semiconductor device use a polyimide resin having excellent heat resistance, electrical characteristics, mechanical characteristics, and the like. The polyimide resin has recently been used as a photosensitive polyimide precursor composition. The photosensitive polyimide precursor composition can be easily coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and heat-imidized, to thereby form a surface protective layer, an interlayer insulating film, and the like.
Accordingly, the photosensitive polyimide precursor composition may remarkably shorten processing time compared with a conventional non-photosensitive polyimide precursor composition.
The photosensitive polyimide precursor composition can be applied as a positive type in which an exposed part is developed and dissolved or as a negative type in which the exposed part is cured and maintained. The positive type photosensitive polyimide precursor composition is preferably used, since a non-toxic alkali aqueous solution is used as a development solution. The positive photosensitive polyimide precursor composition includes a polyimide precursor of polyamic acid, a photosensitive material of diazonaphthoquinone, and the like.
However, the positive photosensitive polyimide precursor composition may not provide the desired pattern because the carboxylic acid of the polyamic acid is too highly soluble in an alkali. In order to solve this problem, the carboxylic acid can be replaced with phenolic hydroxyl acid, for example, by esterificating the polyamidic acid with an alcohol compound having at least one hydroxyl group. See Japanese Patent Laid-Open Publication No. H10-30739. This material, however, can be insufficiently developed and can exhibit film loss or resin delamination from a substrate.
Recently, another material prepared by mixing the polybenzoxazole precursor with a diazonaphthoquinone compound has drawn attention (Japanese Patent Laid-open Publication No. S63-96162). However, when actually used as the polybenzoxazole precursor composition, film loss of an unexposed part is remarkably increased, and the desirable pattern may not be obtained after development.
In order to improve this problem, if the molecular weight of the polybenzoxazole precursor is increased, the film loss of the unexposed part can be reduced. A residue (a scum), however, can be generated during development, which can deteriorate resolution and increase development time on the exposed part.
In order to solve the problem, addition of a certain phenol compound to a polybenzoxazole precursor composition has been reported to suppress film loss in unexposed parts during development (Japanese Patent Laid-Open Publication No. H9-302221 and Japanese Patent Laid-Open Publication No. 2000-292913). However, the suppression of the film loss in unexposed parts is insufficient.
Accordingly, research on increasing the suppression of the film loss as well as preventing generation of the development residue (scum) is required. In addition, research on a dissolution-inhibiting agent is required, since a phenol compound used to adjust solubility can decompose at a high temperature during curing, can cause a side reaction, and the like and as a result, can damage the mechanical properties of a cured film.
The positive photosensitive resin composition including a polybenzoxazole precursor may also be applied to an organic insulating film or a barrier rib material in the field of display devices. For example, a liquid crystal display can have advantages such as lightness, thinness, low cost, low power consumption for operation, excellent adherence to an integrated circuit, and the like and is increasingly used in laptop computers, monitors, and TV screens.
The liquid crystal display includes a lower substrate having a black matrix, a color filter, and an ITO pixel electrode, an active circuit portion including a liquid crystal layer, a thin film transistor, and a capacitor layer, and an upper substrate having an ITO pixel electrode.
With regard to recently developed organic light emitting diodes (OLEDs), each organic light emitting element is arranged as pixels in a matrix format. These pixels may be arranged to emit the same color and fabricate a single color display, or arranged into three primary colors of red (R), green (G), and blue (B) to emit various colors.